In this study a He DC atmospheric pressure glow discharge (APGD) is characterized under dry conditions and with the introduction of wet aerosols. The aerosols are generated by a conventional pneumatic nebulization system using a MicroMist nebulizer placed in a double pass spray chamber according to Scott or alternatively by a custom-built drop-on-demand (DOD) system based on printer cartridges. The experiments are performed at a He gas flow of 500 mL min−1 and 40 mA current. The influences of the H2O load on the discharge rotational temperature (Trot), excitation temperature (Texc) and the electron number density (ne) are determined. Temperature reductions when comparing dry and wet conditions are found to be around 500 K for the Trot and 240–400 K for the Texc. Detection limits for the elements Cd, Cu, Mg, Mn and Na are presented for pneumatic nebulization coupled to a continuous flow injection system. They are found to be between 10 μg L−1 for Na and 140 μg L−1 for Cu. In the case of the drop-on-demand system a value of 16 μg L−1 for Na was obtained. The applicability of the discharge to the determination of Na in a tap water sample at concentration levels of 20 mg L−1 is shown for both introduction systems and the accuracy of the results is found to be within 1.3 mg L−1 as compared to the result of inductively coupled plasma optical emission spectrometry (ICP-OES).

•All mobile sub-surface and depth-profiling techniques for paintings are reviewed.•The number of techniques available has increased considerably in the last years.•X-ray radiography and infrared reflectography are still the most used techniques.•Scanning macro-XRF and optical coherence tomography begin to establish.•Industrial non destructive testing techniques support the preservation of paintings.Hidden, sub-surface paint layers and features contain valuable information for the art-historical investigation of a painting's past and for its conservation for coming generations. The number of techniques available for the study of these features has been considerably extended in the last decades and established techniques have been refined.This review focuses on mobile non-destructive subsurface imaging and depth profiling techniques, which allow for the in-situ investigation of easel paintings, i.e. paintings on a portable support.Among the techniques discussed are: X-ray radiography and infrared reflectography, which are long established methods and are in use for several decades. Their capabilities of element/species specific imaging have been extended by the introduction of energy/wavelength resolved measurements.Scanning macro-X-ray fluorescence analysis made it for the first time possible to acquire elemental distribution images in-situ and optical coherence tomography allows for the non-destructive study the surface paint layers in virtual cross-sections.These techniques and their variants are presented next to other techniques, such as Terahertz imaging, Nuclear Magnetic Resonance depth profiling and established techniques for non destructive testing (thermography, ultrasonic imaging and laser based interference methods) applied in the conservation of historical paintings.Next to selected case studies the capabilities and limitations of the techniques are discussed.

In this work the depth-profile analysis of thermoelectric layers deposited on Au and Cr covered Si wafers with the aid of pulsed radiofrequency glow discharge time-of-flight mass spectrometry (pulsed RF-GD-TOFMS also called plasma profiling TOFMS (PP-TOFMS™)) is described. For thermoelectric materials the depth resolutions obtained with both PP-TOFMS and secondary ion mass spectrometry (SIMS) are shown to be well comparable and in the order of the roughness of the corresponding layers (between 20 and 3700 nm). With both methods a direct solid analysis without any preparation steps is possible. In addition, the analysis of the samples with PP-TOFMS proved to be faster by a factor of 26 compared to SIMS, as sputtering rates were found to be 80 nm s− 1 and 3 nm s− 1, respectively.For the analyzed samples the results of PP-TOFMS and SIMS show that a homogeneous deposition was obtained. Quantitative results for all samples could also be obtained directly by PP-TOFMS when the stoichiometry of one sample was determined beforehand for instance by inductively coupled plasma optical emission spectrometry (ICP-OES) and scanning electron microscopy energy dispersive X-ray fluorescence spectrometry (SEM-EDX). For Bi2Te3 the standard deviation for the main component concentrations within one sample then is found to be between 1.1% and 1.9% and it is 3.6% from sample to sample. For Sb2Te3 the values within one sample are from 1.7% to 4.2% and from sample to sample 5.3%, respectively.Highlights► Depth resolution in sub micrometer size by glow discharge mass spectrometry. ► Bi and Sb telluride layers composition with GD-TOF-MS, ICP-OES and SEM-EDX agree. ► Homogeneities of layers measured with GD-TOF-MS and SIMS agree.

In this work, an analytical procedure for determinations of the main components with inductively coupled plasma optical emission spectrometry (ICP-OES) in the case of thermoelectric materials is described, which is used to optimize the production of electrochemically deposited thermoelectric films on the basis of Bi2Te3 and Sb2Te3. To correct for flicker noise caused signal fluctuations or drifts the use of internal and external standards is evaluated. When the precision cannot be improved by their application the simultaneous detection of several emission lines of one element allows the correction for statistical noise. With principal component regression (PCR) and pooled regression, the reduction of statistical noise is demonstrated. It will be shown that in average a lowering of the limits of quantification (LOQ) and even more important, a reduction of error bands, namely the confidence intervals, for the given amounts of samples of as few as 0.1 mg down to the 1% level can be achieved.

The possibilities of a helium microstrip microwave induced plasma, operated at less than 40 W and less than 250 mL min−1 of gas, as source for optical emission spectrometry (MSP-OES) were studied for the element specific detection of halogenated volatile organic compounds, such as chlorinated and brominated alkanes and arenes, after their separation by capillary gas chromatography (GC). After hyphenation of the GC with MSP-OES with the aid of a heated transfer line, different gas chromatographic parameters, like the carrier gas flow (1.4–3.3 mL min−1) and the oven temperature (100–200), as well as different plasma specific parameters, like the forward power (30–40 W) and the plasma gas flow (100–200 mL min−1), were optimized. In the next step, rotational and excitation temperatures of microstrip plasma were studied in dependence on analyte concentrations between 1 and 10% v/v in pentane and found to be in the order of 1250–1650, as measured with OH bands, and 6100–6900 K, as measured with Fe-lines from ferrocene vapor entered in the plasma gas, respectively. Further, it could be shown that the hyphenated technique GC-MSP-OES can be used for the determination of volatile halogenated organic compounds under the use of an internal standard with recovery rates at the order of 90–110% at the 2–5 mg g−1 level. The absolute limits of detection for volatile halogenated organic compounds, obtained with GC-MSP-OES and the Cl I 837.594 nm, Br I 827.244 nm and C I 247.856 nm, were found to be in the ng-range and the relative detection limits in pentane in the µL L−1 range.

The use of direct current arc atomic emission spectrometry (DC-arc-AES) with a CCD spectrometer for the direct determination of the trace impurities Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr in three well characterized boron carbide powders is described. The detection limits obtained by the procedure were found to be between 0.2 (Mg) and 25 (Na) μg g−1 for the above elements. Three boron carbide powder samples with trace element concentrations between 0.9 (Cu) and 934 (Si) μg g−1 for Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr — including the standard reference material ERM®-ED102 — were analyzed by DC-arc-AES. The relative standard deviations for 9 measurements when using 5.0 ± 0.3 mg of the respective samples were found to vary from 6.2 to 27% for Al and Cu, respectively. The trace elements Al, Ca, Cr, Cu, Fe, Mn, Ni, Si, Ti and Zr could be determined in the standard reference material and their concentrations determined by DC-arc AES were found to be between 89 and 116% of the accepted values. Fe and Ti were determined by DC-arc AES in the three boron carbide samples as well as in Al2O3, BN, SiC, coal fly ash, graphite and obsidian rock. The correlation coefficients of the plots of the net intensities versus the accepted values over the concentration ranges from 18 to 1750 and from 6 to 8000 μg g−1 are 0.999 and 0.990 for Fe and Ti, respectively.

In this study a new DC-APGD operated in He was developed and characterized. The discharge is operated at 0.9 kV and about 25–35 mA and at a gas flow of 100 ml/min. The source was spectroscopically studied and parameters such as the rotational temperature (Trot), the excitation temperature (Texc), the ionization temperature (Tion) and the electron number density (ne) were determined. The current–voltage characteristic of the source was studied as well. At optimized conditions the discharge operates in the normal region of the current–voltage characteristic. Rotational and excitation temperatures determined with the use of OH band and Fe I lines as thermometric species were of the order of about 900–1200 and 4500–5500 K, respectively. This indicates that despite of the atmospheric pressure, the discharge is not in LTE. Spatially resolved temperature measurements were performed with axial as well as radial resolution and showed relatively flat profiles. Axially resolved emission intensity profiles for several species such as H, N2, N2+, OH, He and Hg were determined. It also was found that H2 introduced into the He by electrolysis of acid solutions such as in ECHG considerably increases the spectroscopically measured gas temperatures but decreases the analyte line intensities, as shown for Hg.

The use of slurry sampling electrothermal evaporation inductively coupled plasma optical emission spectrometry (SlS-ETV-ICP-OES) for the direct determination of trace elements in boron carbide powders with different particle size distributions was investigated. It was found that the addition of 6 mL min−1 of Freon R12 (Cl2F2C) to the 500 mL min−1 Ar carrier gas flow as a thermochemical reagent resulted in an increase of the net line intensity for Ti by a factor of 25 in SlS-ETV-ICP-OES, when analyzing 20 μL of a slurry containing 1% of the boron carbide powder BC-1. After heating the dry residue of 20 μL of a slurry of 1% of boron carbide for 12 s to 2600 °C on a L'vov platform the residues on the platforms were analyzed by total reflection X-ray fluorescence spectrometry (TXRF). The evaporation efficiency for Ti was found to have increased from 12 to 97% by the addition of 6 mL min−1 of R12 as compared to evaporation in Ar only. When heating dry residues of boron carbide slurries on L'vov platforms to temperatures ranging from 2000 to 2600 °C without adding R12 to the Ar, it could be observed visually that only a small fraction of the boron carbide matrix is evaporated. However, when heating at 2600 °C under the addition of R12 almost no residues were found on the platform after the evaporation step. For the analysis of boron carbide powders with SlS-ETV-ICP-OES the limits of detection were found to be between 0.002 and 2 μg g−1 for the elements Al, Ca, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni and Ti. For Fe a wide variety of samples could be analyzed by SlS-ETV-ICP-OES with one calibration under the use of R12. This was shown for different samples, namely three boron carbide powders, three boron nitride powders, an aluminium oxide powder (NIST 699), silicon carbide powder (BAM S-003), powdered apple leaves (NIST 1515), a reference sample for trace elements in natural water (NIST 1643d) and an aqueous standard solution. When plotting the net line intensities versus the accepted concentrations a coefficient of determination of 0.990 is obtained. By SlS-ETV-ICP-OES under the addition of R12 the values obtained were found to be between 78 to 128% of the mean of the results of slurry sampling-TXRF and of ICP-OES subsequent to wet chemical digestion. 11 trace elements with concentrations ranging from 0.7 to 370 μg g−1 for Co and Fe, respectively, could be determined in two boron carbide powders with particle size distributions of d90 = 3.5 μm and d90 = 9.2 μm, respectively.

The use of slurry sampling total reflection X-ray fluorescence spectrometry (SlS-TXRF) for the direct determination of Ca, Cr, Cu, Fe, Mn and Ti in four boron nitride powders has been described. Measurements of the zeta potential showed that slurries with good stabilities can be obtained by the addition of polyethylenimine (PEI) at a concentration of 0.1 wt.% and by adjusting the pH at 4. For the optimization of the concentration of boron nitride in the slurries the net line intensities and the signal to background ratios were determined for the trace elements Ca and Ti as well as for the internal standard element Ga in the case of concentrations of boron nitride ranging from 1 to 30 mg mL−1. As a compromise with respect to high net line intensities and high signal to background ratios, concentrations of 5 mg mL−1 of boron nitride were found suitable and were used for all further measurements. The limits of detection of SlS-TXRF for the boron nitride powders were found to range from 0.062 to 1.6 μg g– 1 for Cu and Ca, respectively. Herewith, they are higher than those obtained in solid sampling and slurry sampling graphite furnace atomic absorption spectrometry (SoS-GFAAS, SlS-GFAAS) as well as those of solid sampling electrothermal evaporation inductively coupled plasma optical emission spectrometry (SoS-ETV-ICP-OES). For Ca and Fe as well as for Cu and Fe, however, they were found to be lower than for GFAAS and for ICP-OES subsequent to wet chemical digestion, respectively. The universal applicability of SlS-TXRF to the analysis of samples with a wide variety of matrices could be demonstrated by the analysis of certified reference materials such as SiC, Al2O3, powdered bovine liver and borate ore with a single calibration. The correlation coefficients of the plots for the values found for Ca, Fe and Ti by SlS-TXRF in the boron nitride powders as well as in the before mentioned samples versus the reference values for the respective samples over a concentration range from 2.5 to 1470 μg g– 1 were found to be 0.995, 0.991 and 0.997, respectively.

The direct determination of Ca, Co, Cr, Cu, Fe, Mn, Ni and Ti in boron carbide powders with different particle size distributions by means of slurry sampling total reflection X-ray fluorescence spectrometry (TXRF) has been described. The stability of the slurries was monitored by measuring the zeta potential for different pH values and different concentrations of polyethylenimine (PEI). It was found to have a maximum for a PEI concentration of 0.1% and a pH of 4, which were the conditions of the highest stability of the slurries selected for all further measurements. The slurry concentration for the TXRF measurements was optimized with respect to the net intensity and to the signal-to-background ratio for the trace analytes Ca and Ti and for the internal standard Ga. For dry slurry residues of 150 µg boron carbide, the signal-to-background ratios were found to be maximum and to be 5, 23 and 100 for 13.7 ng Ca, 29.1 ng Ti and 15 ng Ga, respectively. For calibration, the addition of Ga to the slurry up to a concentration of 1 µg mL−1 and the use of the Fe present in the sample as internal standard were investigated. Both approaches gave results in TXRF, which are in good agreement with the results of ICP-OES subsequent to wet chemical digestion at the 2 to 1200 µg g−1 concentration level for Ca, Co, Cr, Cu, Fe, Mn, Ni and Ti. The detection limits for these elements in TXRF were found to range from 0.1 to 1.2 µg g−1, and excepted for Ca and Mn, they are in the same range as those for ICP-OES after wet chemical digestion. The relative standard deviations, in the case of the finest powder, range from 1.9% for Ca to 18% for Cr and the average of the relative standard deviations for all elements determined is 9.2%. The correlation coefficients of the determinations of Fe and Ti in seven different boron carbide powders by ICP-OES and TXRF with R = 0.996 and R = 0.997, respectively, were found to be practically equal.

The production of polymeric calibration standard materials with sufficient homogeneity for the calibration of analytical methods with high lateral resolution like LA-ICP-MS was investigated. An index η* was introduced to compare the homogeneities of different acrylonitrile butadiene styrene terpolymer (ABS) based samples. It was demonstrated, that elements present in organic compounds could be introduced into polymeric materials with a higher homogeneity than inorganic compounds without special treatment. For organic Br compounds, a 20 to 30 times higher value for η* was found than it was for the case of AgBr. For Pb stearate and Pb acetate, 10 times higher values for η* were found than was the case for PbCrO4. For PbO, it is shown that multiple extrusion and mechanical treatment can improve the homogeneity of certain inorganic compounds as particle sizes are decreased during the extrusion.

The use of a so-called T-shaped cross-flow nebulizer (T-CFN), which is a modified cross-flow nebulizer with an additional solution introduction channel, has been described for elemental determinations in organic solutions by inductively coupled plasma-optical emission spectrometry using aqueous solutions for calibration. With this nebulizer, the simultaneous generation of an aerosol from a kerosene and from an aqueous solution was possible, a mixed aqueous/organic solution aerosol can be directly formed in the spray chamber and carried to the plasma without the use of a surfactant. The additive properties of the analyte signals were demonstrated, as well as the constancy of the intensity ratios for analyte and reference element lines. These ratios, however, were found to be not significantly different when the analytes were introduced in the plasma via the aqueous or via the organic solution. Therefore, a calibration by standard addition could be carried out in an on-line way after determining the relative efficiency of the nebulization of both solutions. So as to minimize the effect of drifts and fluctuations in the set-up, the instantaneous value of the efficiency of the nebulization was monitored by calculating the line intensity ratio of the so-called reference and auxiliary elements. For analysis, 200 mg of oil standard sample containing 5 mg g−1 of Ba, Ca, Mg, P and Zn were diluted with kerosene up to a volume of 50 mL and the calibration was done with aqueous standard solutions using the T-CFN. The limits of detection in solution of Ba, Ca, Mg, P and Zn obtained for the simultaneous nebulization of kerosene and aqueous solutions were, respectively, 7, 13, 4, 51 and 7 μg L−1 and were found to be not higher, by a factor of 10, for the investigated lines when separately analyzing kerosene and aqueous solutions with a conventional cross-flow nebulizer. Ca, P and Zn were determined in the same way in two further oil samples at the mg g−1 level. The results of the analysis for the oil samples mentioned before were found to be in good agreement, respectively, with the certified values and with those obtained in an inter-laboratory test.

A 2.45 GHz low power microwave microstrip plasma (MSP) exiting the wafer and operated with Ar at atmospheric pressure was used for the optical emission spectrometric determination of Hg with the aid of a miniaturized optical fiber spectrometer with a CCD detector and the cold vapor (CV) generation technique using NaBH4 and SnCl2 as reductants. The experimental conditions were optimized with respect to the relative intensity of the Hg I 253.6 nm line and its signal-to-background intensity ratio (SBR). So as to understand the results of the optimization experiments, the excitation temperatures as measured from Ar I lines (Texc) and the electron number densities (ne) for the Ar MSP loaded with Hg vapors were determined and found to be in the range from 5500 to 6300 K and from 1.4 to 2.0 × 1014 cm−3, respectively. Under the optimized conditions, the detection limit for Hg of the CV-MSP-OES using SnCl2 as the reducing agent was found to be much lower (0.11 ng mL−1) than in the case where NaBH4 was used (9 ng mL−1). The linearity range was found to be up to 1 µg mL−1 while the precision was of the order of 0.7–5%. The procedure with SnCl2 as reductant was used for the determination of Hg at a concentration of 0.2 µg mL−1 in synthetic water samples containing 1 to 4% (m/v) of NaCl with an accuracy of 3% as well as in a solution of the domestic sludge standard reference material (NIST SRM 2781) with a certified concentration for Hg of 3.64 ± 0.25 µg g−1 for which 3.55 ± 0.41 µg g−1 was found.

Continuous flow generation of Br2, Cl2 and H2S coupled to a low-power 2.45 GHz microwave microstrip He plasma exiting from a capillary gas channel in a micro-fabricated sapphire wafer with microstrip lines has been used for the optical emission spectrometric determination of Br, Cl and S using a miniaturized optical fiber CCD spectrometer. Under optimized conditions, detection limits (3σ) of 330, 190 and 220 μg l− 1 for Br, Cl and S, respectively, under the use of the Br II 478.5 nm, Cl I 439.0 nm and S I 469.0 nm lines were obtained and the calibration curves were found to be linear over 2 orders of magnitude. In addition, when introducing CO2 and using the rotational line of the CN molecular band at 385.7 nm the detection limit for C was 4.6 μg l− 1. The procedure developed was found to be free from interferences from a number of metal cations and non-metal anions. Only the presence of CO32− and CN− was found to cause severe spectral interferences as strong CN and C2 molecular bands occurred as a result of an introduction of co-generated CO2 and HCN into the plasma. With the procedure described Br, Cl and S could be determined at a concentration level of 10–30 mg l− 1 with accuracy and precision better than 2%.

Continuous flow chemical hydride generation coupled directly to a 40 W, atmospheric pressure, 2.45 GHz microwave microstrip Ar plasma operated inside a capillary channel in a sapphire wafer has been optimized for the emission spectrometric determination of As and Sb. The effect of the NaBH4 concentration, the concentration of HCl, HNO3 and H2SO4 used for sample acidification, the Ar flow rate, the reagent flow rates, the liquid volume in the separator as well as the presence of interfering metals such as Fe, Cu, Ni, Co, Zn, Cd, Mn, Pb and Cr, was investigated in detail. A considerable influence of Fe(III) (enhancement of up to 50 %) for As(V) and of Fe(III), Cu(II) and Cr(III) (suppression of up to 75%) as well as of Cd(II) and Mn(II) (suppression by up to 25%) for Sb(III) was found to occur, which did not change by more than a factor of 2 in the concentration range of 2–20 μg ml− 1. The microstrip plasma tolerated the introduction of 4.2 ml min− 1 of H2 in the Ar working gas, which corresponded to an H2/Ar ratio of 28%. Under these conditions, the excitation temperature as measured with Ar atom lines and the electron number density as determined from the Stark broadening of the Hβ line was of the order of 5500 K and 1.50 · 1014 cm− 3, respectively. Detection limits (3σ) of 18 ng ml− 1 for As and 31 ng ml− 1 for Sb were found and the calibration curves were linear over 2 orders of magnitude. With the procedure developed As and Sb could be determined at the 45 and 6.4 μg ml− 1 level in a galvanic bath solution containing 2.5% of NiSO4. Additionally, As was determined in a coal fly ash reference material (NIST SRM 1633a) with a certified concentration of As of 145 ± 15 μg g− 1 and a value of 144 ± 4 μg g− 1 was found.

A neutron-activated Al2O3 powder SRM 699 (NIST) containing the γ-radiation emitting radionuclides 51Cr, 59Fe, 60Co and 65Zn has been used to study the influence of thermochemical reagents on the volatilization and transport efficiency for these trace elements in electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) of Al2O3 powders. From the signals in the γ-spectra for the radiotracers it has been found that less than 2% of the elements Cr, Fe, Co and Zn is left back in a graphite furnace from Al2O3 powders at 2200 °C even without addition of a thermochemical reagent and the latter even was found to decrease the volatilization efficiencies. The recovery for the radiotracers on filters at the end of the transport tube as measured from the signals in the γ-spectra, however, was found to increase in most cases (i.e. from about 10% to more than 20%) when Pd(NO3)2, Pd(NO3)2 + Mg(NO3)2, PdCl2, IrCl3, SnCl2, AgCl, NaF, NH4Cl and NH4F were added at amounts generally used in electrothermal vaporization inductively coupled plasma mass spectrometry. However, when adding higher amounts as stoichiometrically required for a complete halogenation of the sample matrix in the case of AgCl, C8F15O2Na, IrCl3 or PdCl2 the transport efficiencies considerably decrease again. As shown in the case of NH4Cl the amount of thermochemical reagent used has to be optimized so as to obtain maximum analyte transport efficiencies. A comparison of the influence of NH4Cl on the transport efficiencies with its influence on the ETV-ICP-MS signals for Fe demonstrates the importance of transport efficiency changes for the effects of thermochemical reagents in electrothermal vaporization inductively coupled plasma mass spectrometry.

The use of a so-called trihedral and a T-shaped cross-flow pneumatic nebulizer with dual solution loading for inductively coupled plasma optical emission spectrometry has been studied. By these devices analyte clouds from two solutions can be mixed during the aerosol generation step. For both nebulizers the correction of matrix effects using internal standardization and standard addition calibration in an on-line way was investigated and compared to elemental determinations using a conventional cross-flow nebulizer and calibration with synthetic standard solutions without matrix matching. A significant improvement of accuracy, both for calibration with internal standardization and standard addition, was obtained in the case of four synthetic solutions containing each 40 mmol L− 1 Na, K, Rb and Ba as matrix elements and 300 μg L− 1 Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb as analytes. Calibration by standard addition in the case of dual solution loading has been shown to be very useful in the determination of elements at minor and trace levels in steel and alumina reference materials. The results of analysis for minor concentrations of Cr, Cu and Ni in steel as well as for Ca, Fe, Ga, Li, Mg, Mn, Na, Si and Zn in alumina powder certified reference materials subsequent to sample dissolution were found to be in good agreement with the certificates. Limits of detection were found to be only slightly above those for a conventional cross-flow nebulizer and a precision better than 3% was realized with both novel nebulizers.

The suitability of a 2.45-GHz atmospheric pressure, low-power microwave microstrip plasma (MSP) operated with Ar and He for the determination of Hg by continuous-flow cold vapor (CV) generation, using SnCl2/HCl as the reducing agent, and optical emission spectrometry (OES) using a small CCD spectrometer was studied. The areas of stability for a discharge in the Ar and in the He MSP enclosed in a cylindrical channel in a quartz wafer were investigated. The excitation temperatures as measured for discharge gas atoms (Ar I, He I), and the electron number densities at 35–40 W and 15–400 mL min−1 were found to be at the order of 3,200–5,500 K and 0.8 × 1014–1.6 × 1014 cm−3, respectively. The relative intensity of the Hg I 253.6-nm line and the signal-to-background ratio as a function of the forward power (35–40 W) as well as of the flow rate of the working gas (15–400 mL min−1) were evaluated and discussed. For the selected measurement conditions, the Ar MSP was established to have the lower detection limit for Hg (0.6 ng mL−1) compared with the He MSP. The linearity range is up to 300 ng mL−1 and the precision is on the order of 1–3%. With the optimized CV Ar MSP-OES method a determination of Hg in spiked domestic and natural waters at concentration levels of 20–100 μg L−1 and an accuracy of 1–4% could be performed. In an NIST domestic sludge standard reference material, Hg (3.64 μg g−1) could be determined with a relative standard deviation of 4% and an agreement better than 4%.

An electrothermal vaporization (ETV) system useful for the analysis of solutions and slurries has been coupled with a sector-field inductively coupled plasma mass spectrometer (ICP–MS) equipped with an array detector. The ability of this instrument to record the transient signals produced for a number of analytes in ETV–ICP–MS is demonstrated. Detection limits for Mn, Fe, Co, Ni, Cu, Zn and Ga are in the range of 4–60 pg μL− 1 for aqueous solutions and in the low μg g− 1 range for the analysis of 10 mg mL− 1 slurries of Al2O3 powders. The dynamic ranges measured for Fe, Cu and Ga spanned 3–5 orders of magnitude when the detector was operated in the low-gain mode and appear to be limited by the ETV system. Trace amounts of Fe, Cu and Ga could be directly determined in Al2O3 powders at the 2–270 μg g− 1 level without the use of thermochemical reagents. The results well agree with literature values for Fe and Cu, whereas deviations of 50% at the 90 μg g− 1 level for Ga were found.

The determination of trace concentrations of As and its species in water and sediment samples by the use of microwave plasma torch optical emission spectrometry (MPT-OES) and chemical (CHG) as well as different electrochemical hydride generation (EcHG) systems was studied, when using Ar and He as working gases for the microwave plasmas. Under optimized conditions and with He as working gas the detection limits (3σ) for As (228.82 nm) were found to be 21 and 13 μg/l for chemical and electrochemical hydride generation, respectively. When Ar is used as working gas, the detection limits are higher, i.e., 60 and 48 μg/l for chemical and electrochemical hydride generation, respectively. Several miniaturized electrochemical hydride generation cells, among which some use glassy carbon foam and carbon fiber for the cathode, were used and the detection limits with these systems were found to be by a factor of 3–5 higher than in the conventional electrochemical hydride generation cell. The effects of Ca, Fe, Bi, Se, etc., on the determination of As with chemical and miniaturized electrochemical hydride generation systems were studied, and it was found that the interferences in electrochemical hydride generation were lower than in chemical hydride generation. The efficiency of the generation of AsH3 in chemical hydride generation and all electrochemical hydride generation systems, as determined by a coulometric titration of the remaining As(III) in the waste solutions of the gas–liquid separator, was found to be below 18% to 90%, depending on the cells. A modified graphite furnace (GF) unit was coupled to the hydride generation system for hot-trapping of the hydride forming elements. When trapping the AsH3 produced in a miniaturized electrochemical hydride generation system on Pd in a graphite furnace and sweeping the As into the He microwave plasma torch, the detection limit for As could be improved to 1.7 μg/l (improvement by a factor of 14). The procedure without trapping could be used for the determination of As in a standard reference water (SRM 1643d) containing 56.02±0.73 mg/l of total As within an experimental error of 8%. With the miniaturized electrochemical hydride generation and microwave plasma torch emission spectrometry in the case of trapping the total As could be determined in Saxony river sediment samples and in Hungarian spring water samples at the 10–30 and 50–360 μg/l levels, respectively.

A modified compact 2.45 GHz microstrip plasma (MSP) operated with Ar as working gas at atmospheric pressure has been characterized and examined for its suitability for the determination of Hg as gaseous species by optical emission spectrometry. As a formerly described MSP the new device is provided on a sapphire substrate. The areas of plasma stability in terms of gas flow rates and microwave power for both MSPs with respect to plasma form and reflected power were investigated. Power levels of 5–40 W and Ar flow rates of 15–60 l/h were used. The modified MSP, which extends out of the channel in the sapphire substrate, was used for the recording of emission spectra for Hg vapor at different working conditions. Using optimized parameters a detection limit for Hg of less than 10 ng Hg/l Ar is obtained. The attainable excitation temperatures in the modified MSP at different microwave power were determined under the use of Fe as thermometric species and introducing ferrocene into the plasma. They were found to be at the order of 6000–7000 K for a power of 10–40 W and a gas flow of 15 l/h. It was shown that the modified MSP source can be combined with both a conventional monochromator with photomultiplier detection and a miniaturized spectrometer with CCD detection, whereby space–angle limitations are not stringent.

A procedure based on electrothermal evaporation (ETV) and inductively coupled plasma atomic emission spectrometry (ICP-OES) for the determination of trace impurities in Al2O3 powders without any sample pretreatment is presented. With the aid of matrix modifier the transport and the evaporation efficiency for refractory compounds could be increased by forming halides with a lower boiling point. As calibration is still a problem in direct solid sample analysis, different calibration approaches including the use of certified reference materials from NIST and standard addition of aqueous solutions of analytes were discussed. The accuracy obtained with calibration and with the standard addition method was shown up for the elements Ca, Fe, Ga, Mg, Mn, Na, Ni and V for the case of Al2O3 NIST standard reference material (SRM 699). The ETV–ICP-OES method was used for the analysis of Al2O3 powders with impurities in the low μg/g range and the results for the elements Ca, Fe, Ga, Mg, Mn, Na, Ni and V obtained with evaporation of discrete powder amounts with ETV–ICP-OES and slurry evaporation under the use of ultrasonic homogenization during the sampling and ETV–ICP-MS were shown to be in a good agreement.

The possibilities of a helium microstrip microwave induced plasma, operated at less than 40 W and less than 250 mL min−1 of gas, as source for optical emission spectrometry (MSP-OES) were studied for the element specific detection of halogenated volatile organic compounds, such as chlorinated and brominated alkanes and arenes, after their separation by capillary gas chromatography (GC). After hyphenation of the GC with MSP-OES with the aid of a heated transfer line, different gas chromatographic parameters, like the carrier gas flow (1.4–3.3 mL min−1) and the oven temperature (100–200), as well as different plasma specific parameters, like the forward power (30–40 W) and the plasma gas flow (100–200 mL min−1), were optimized. In the next step, rotational and excitation temperatures of microstrip plasma were studied in dependence on analyte concentrations between 1 and 10% v/v in pentane and found to be in the order of 1250–1650, as measured with OH bands, and 6100–6900 K, as measured with Fe-lines from ferrocene vapor entered in the plasma gas, respectively. Further, it could be shown that the hyphenated technique GC-MSP-OES can be used for the determination of volatile halogenated organic compounds under the use of an internal standard with recovery rates at the order of 90–110% at the 2–5 mg g−1 level. The absolute limits of detection for volatile halogenated organic compounds, obtained with GC-MSP-OES and the Cl I 837.594 nm, Br I 827.244 nm and C I 247.856 nm, were found to be in the ng-range and the relative detection limits in pentane in the µL L−1 range.

The use of a so-called T-shaped cross-flow nebulizer (T-CFN), which is a modified cross-flow nebulizer with an additional solution introduction channel, has been described for elemental determinations in organic solutions by inductively coupled plasma-optical emission spectrometry using aqueous solutions for calibration. With this nebulizer, the simultaneous generation of an aerosol from a kerosene and from an aqueous solution was possible, a mixed aqueous/organic solution aerosol can be directly formed in the spray chamber and carried to the plasma without the use of a surfactant. The additive properties of the analyte signals were demonstrated, as well as the constancy of the intensity ratios for analyte and reference element lines. These ratios, however, were found to be not significantly different when the analytes were introduced in the plasma via the aqueous or via the organic solution. Therefore, a calibration by standard addition could be carried out in an on-line way after determining the relative efficiency of the nebulization of both solutions. So as to minimize the effect of drifts and fluctuations in the set-up, the instantaneous value of the efficiency of the nebulization was monitored by calculating the line intensity ratio of the so-called reference and auxiliary elements. For analysis, 200 mg of oil standard sample containing 5 mg g−1 of Ba, Ca, Mg, P and Zn were diluted with kerosene up to a volume of 50 mL and the calibration was done with aqueous standard solutions using the T-CFN. The limits of detection in solution of Ba, Ca, Mg, P and Zn obtained for the simultaneous nebulization of kerosene and aqueous solutions were, respectively, 7, 13, 4, 51 and 7 μg L−1 and were found to be not higher, by a factor of 10, for the investigated lines when separately analyzing kerosene and aqueous solutions with a conventional cross-flow nebulizer. Ca, P and Zn were determined in the same way in two further oil samples at the mg g−1 level. The results of the analysis for the oil samples mentioned before were found to be in good agreement, respectively, with the certified values and with those obtained in an inter-laboratory test.

The production of polymeric calibration standard materials with sufficient homogeneity for the calibration of analytical methods with high lateral resolution like LA-ICP-MS was investigated. An index η* was introduced to compare the homogeneities of different acrylonitrile butadiene styrene terpolymer (ABS) based samples. It was demonstrated, that elements present in organic compounds could be introduced into polymeric materials with a higher homogeneity than inorganic compounds without special treatment. For organic Br compounds, a 20 to 30 times higher value for η* was found than it was for the case of AgBr. For Pb stearate and Pb acetate, 10 times higher values for η* were found than was the case for PbCrO4. For PbO, it is shown that multiple extrusion and mechanical treatment can improve the homogeneity of certain inorganic compounds as particle sizes are decreased during the extrusion.

The direct determination of Ca, Co, Cr, Cu, Fe, Mn, Ni and Ti in boron carbide powders with different particle size distributions by means of slurry sampling total reflection X-ray fluorescence spectrometry (TXRF) has been described. The stability of the slurries was monitored by measuring the zeta potential for different pH values and different concentrations of polyethylenimine (PEI). It was found to have a maximum for a PEI concentration of 0.1% and a pH of 4, which were the conditions of the highest stability of the slurries selected for all further measurements. The slurry concentration for the TXRF measurements was optimized with respect to the net intensity and to the signal-to-background ratio for the trace analytes Ca and Ti and for the internal standard Ga. For dry slurry residues of 150 µg boron carbide, the signal-to-background ratios were found to be maximum and to be 5, 23 and 100 for 13.7 ng Ca, 29.1 ng Ti and 15 ng Ga, respectively. For calibration, the addition of Ga to the slurry up to a concentration of 1 µg mL−1 and the use of the Fe present in the sample as internal standard were investigated. Both approaches gave results in TXRF, which are in good agreement with the results of ICP-OES subsequent to wet chemical digestion at the 2 to 1200 µg g−1 concentration level for Ca, Co, Cr, Cu, Fe, Mn, Ni and Ti. The detection limits for these elements in TXRF were found to range from 0.1 to 1.2 µg g−1, and excepted for Ca and Mn, they are in the same range as those for ICP-OES after wet chemical digestion. The relative standard deviations, in the case of the finest powder, range from 1.9% for Ca to 18% for Cr and the average of the relative standard deviations for all elements determined is 9.2%. The correlation coefficients of the determinations of Fe and Ti in seven different boron carbide powders by ICP-OES and TXRF with R = 0.996 and R = 0.997, respectively, were found to be practically equal.

The use of slurry sampling electrothermal evaporation inductively coupled plasma optical emission spectrometry (SlS-ETV-ICP-OES) for the direct determination of trace elements in boron carbide powders with different particle size distributions was investigated. It was found that the addition of 6 mL min−1 of Freon R12 (Cl2F2C) to the 500 mL min−1 Ar carrier gas flow as a thermochemical reagent resulted in an increase of the net line intensity for Ti by a factor of 25 in SlS-ETV-ICP-OES, when analyzing 20 μL of a slurry containing 1% of the boron carbide powder BC-1. After heating the dry residue of 20 μL of a slurry of 1% of boron carbide for 12 s to 2600 °C on a L'vov platform the residues on the platforms were analyzed by total reflection X-ray fluorescence spectrometry (TXRF). The evaporation efficiency for Ti was found to have increased from 12 to 97% by the addition of 6 mL min−1 of R12 as compared to evaporation in Ar only. When heating dry residues of boron carbide slurries on L'vov platforms to temperatures ranging from 2000 to 2600 °C without adding R12 to the Ar, it could be observed visually that only a small fraction of the boron carbide matrix is evaporated. However, when heating at 2600 °C under the addition of R12 almost no residues were found on the platform after the evaporation step. For the analysis of boron carbide powders with SlS-ETV-ICP-OES the limits of detection were found to be between 0.002 and 2 μg g−1 for the elements Al, Ca, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni and Ti. For Fe a wide variety of samples could be analyzed by SlS-ETV-ICP-OES with one calibration under the use of R12. This was shown for different samples, namely three boron carbide powders, three boron nitride powders, an aluminium oxide powder (NIST 699), silicon carbide powder (BAM S-003), powdered apple leaves (NIST 1515), a reference sample for trace elements in natural water (NIST 1643d) and an aqueous standard solution. When plotting the net line intensities versus the accepted concentrations a coefficient of determination of 0.990 is obtained. By SlS-ETV-ICP-OES under the addition of R12 the values obtained were found to be between 78 to 128% of the mean of the results of slurry sampling-TXRF and of ICP-OES subsequent to wet chemical digestion. 11 trace elements with concentrations ranging from 0.7 to 370 μg g−1 for Co and Fe, respectively, could be determined in two boron carbide powders with particle size distributions of d90 = 3.5 μm and d90 = 9.2 μm, respectively.

In this work, an analytical procedure for determinations of the main components with inductively coupled plasma optical emission spectrometry (ICP-OES) in the case of thermoelectric materials is described, which is used to optimize the production of electrochemically deposited thermoelectric films on the basis of Bi2Te3 and Sb2Te3. To correct for flicker noise caused signal fluctuations or drifts the use of internal and external standards is evaluated. When the precision cannot be improved by their application the simultaneous detection of several emission lines of one element allows the correction for statistical noise. With principal component regression (PCR) and pooled regression, the reduction of statistical noise is demonstrated. It will be shown that in average a lowering of the limits of quantification (LOQ) and even more important, a reduction of error bands, namely the confidence intervals, for the given amounts of samples of as few as 0.1 mg down to the 1% level can be achieved.

In this study a He DC atmospheric pressure glow discharge (APGD) is characterized under dry conditions and with the introduction of wet aerosols. The aerosols are generated by a conventional pneumatic nebulization system using a MicroMist nebulizer placed in a double pass spray chamber according to Scott or alternatively by a custom-built drop-on-demand (DOD) system based on printer cartridges. The experiments are performed at a He gas flow of 500 mL min−1 and 40 mA current. The influences of the H2O load on the discharge rotational temperature (Trot), excitation temperature (Texc) and the electron number density (ne) are determined. Temperature reductions when comparing dry and wet conditions are found to be around 500 K for the Trot and 240–400 K for the Texc. Detection limits for the elements Cd, Cu, Mg, Mn and Na are presented for pneumatic nebulization coupled to a continuous flow injection system. They are found to be between 10 μg L−1 for Na and 140 μg L−1 for Cu. In the case of the drop-on-demand system a value of 16 μg L−1 for Na was obtained. The applicability of the discharge to the determination of Na in a tap water sample at concentration levels of 20 mg L−1 is shown for both introduction systems and the accuracy of the results is found to be within 1.3 mg L−1 as compared to the result of inductively coupled plasma optical emission spectrometry (ICP-OES).